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Why Does Honey Ferment?
By Rakhee, Founder & Beekeeper at Rantrove Honey. Hands-on beekeeping and raw honey production since 2017.
Quick Answer
Honey ferments when its water content rises above roughly 19%, giving naturally present wild yeast enough moisture to become active and start converting the honey’s sugars into alcohol and carbon dioxide. Well-harvested, properly sealed honey almost never reaches that moisture level, which is why fermentation in good-quality honey is rare — but it can happen if honey is harvested too early, stored with a loose lid, or kept somewhere humid.
Fermented honey is one of those things that sounds alarming the first time you notice it — a jar that’s started fizzing slightly, or smells faintly of alcohol instead of pure sweetness. I don’t get this question as often as the crystallization one, but when I do, it usually comes with a bit of worry attached. So let’s walk through exactly what’s happening, why it’s genuinely uncommon in well-made honey, and what to do if it happens to yours.
What Fermentation Actually Is
Fermentation is what happens when yeast — a naturally occurring microorganism — gets active enough to metabolize sugar and produce alcohol and CO2 as byproducts. It’s the same basic process behind bread, beer, and wine, just happening somewhere you didn’t intend it to.
Honey almost never has this problem naturally, and that’s not an accident. Honey’s low water content and high sugar concentration create what’s called a hostile osmotic environment for microorganisms — in plain terms, there simply isn’t enough available water for yeast to do anything with, even though wild yeast spores are present in trace amounts in nearly all honey.
Why Moisture Content Is the Real Trigger
This is the part that actually matters, and it comes down to a fairly specific number.
Properly ripened raw honey typically sits around 17-18% water content. Below roughly 17.5%, yeast stays dormant — there’s just not enough moisture for it to activate, no matter how long the honey sits on a shelf. Once moisture creeps above about 19%, though, that changes. The yeast wakes up, and given enough time, it starts converting glucose and fructose into ethanol and gas, which is what you’d notice as fizzing, a slightly boozy smell, or a jar that seems to be “working.”
A couple of degrees of moisture percentage might not sound like much, but it’s the entire difference between honey that sits stable for years and honey that starts fermenting within weeks.
What Actually Causes Excess Moisture
In my experience, this comes down to one of three things almost every time:
Harvesting too early. Bees seal, or “cap,” honeycomb cells only once the honey inside has reached the right moisture level through their own fanning and evaporation process. If honey is extracted before enough of the comb is capped — often because a beekeeper is rushing a harvest — the honey simply hasn’t finished dehydrating yet, and it goes into the jar with too much water already in it.
Storage with a loose or open lid. Honey is hygroscopic, meaning it actively absorbs moisture from humid air if it’s not sealed properly. Leaving a jar lid loose, or repeatedly opening it in a humid kitchen, lets ambient moisture creep in over time.
Storing in a high-humidity environment. Even a well-sealed jar can slowly pick up moisture in consistently damp conditions, especially over months.
At Rantrove, we wait until roughly 85% of the comb is capped before extracting for exactly this reason — it’s the bees’ own signal that the honey has reached a stable, low moisture level, and it’s the single biggest thing a beekeeper controls to prevent fermentation before it ever starts.
Is Fermented Honey Safe to Eat?
This is worth being direct about. Mildly fermented honey isn’t typically dangerous in the way spoiled dairy or meat would be — but it’s also not honey doing what it’s supposed to do, and I wouldn’t recommend eating it once fermentation has clearly started.
Signs of fermentation include:
- A slightly fizzy or bubbly texture
- A sour or alcohol-like smell, distinct from honey’s normal sweetness
- Foaming near the surface
- A change in taste toward sour or “off”
If you notice these signs, the safest move is simply not to consume it and instead let your supplier know — a reputable brand will want to hear about it, since it usually points to a harvesting or storage issue worth fixing. It’s a genuinely different situation from crystallization, which is completely normal and doesn’t involve any smell or taste change at all.
Fermentation vs. Crystallization: Don’t Confuse the Two
I bring this up because customers sometimes assume any change in their honey’s texture means something’s wrong, and that’s not the case. Crystallization — honey turning grainy or solid — is a separate, harmless process driven by glucose content, not moisture or yeast. It has no smell change, no fermentation, and no safety concern attached to it whatsoever. Fermentation, by contrast, always comes with that telltale sour or alcohol-like smell. If your honey has simply thickened or turned cloudy with no odor change, that’s crystallization, and it’s completely fine.
How to Prevent Honey From Fermenting at Home
Once honey is properly harvested at the right moisture level, preventing fermentation on your end is mostly about basic storage habits:
- Keep the lid sealed tightly between uses — don’t leave jars open longer than necessary.
- Store in a cool, dry place, away from steam-heavy areas like right next to your stovetop.
- Use a clean, dry spoon every time — introducing moisture (or food particles that carry moisture) via a wet spoon is a common, avoidable cause of contamination.
- Avoid storing honey in the refrigerator, which can actually accelerate crystallization without meaningfully helping against fermentation — room temperature, sealed, is the better default.
Frequently Asked Questions
Can raw honey ferment more easily than processed honey?
Not inherently — fermentation risk comes from moisture content and harvesting timing, not from whether honey is raw or heat-processed. However, some heat-treated commercial honey is pasteurized specifically to kill any yeast present, which does reduce fermentation risk as an added safeguard raw honey doesn’t have. Properly harvested raw honey, with moisture kept low from the start, doesn’t need that step to stay stable.
Does fermented honey taste different?
Yes, distinctly. It typically develops a sour, tangy, or alcohol-like taste that’s easy to tell apart from honey’s normal sweetness, usually alongside a fizzy texture.
Can I still use slightly fermented honey for cooking?
It’s generally not recommended. While the risk is low, fermentation indicates the honey’s composition has changed in ways that affect both quality and intended use — it’s best treated as honey that’s no longer good to eat rather than something to cook around.
How long does honey take to ferment once moisture is too high?
This varies widely based on exact moisture level, ambient temperature, and yeast presence — it can range from a few weeks to several months. There’s no fixed timeline, which is part of why prevention through proper harvesting matters more than trying to “catch it in time.”
Sources & Further Reading:
- National Honey Board — Honey Moisture Content & Quality Standards
- USDA Agricultural Research Service — Honey Composition and Stability Studies
- FSSAI Honey Quality Standards
Written from hands-on beekeeping and honey production experience at Rantrove Honey, sourcing raw, unheated honey directly from our own hives since 2017.